Switching devices, particularly low-voltage switching devices, enable switching of the current paths between an electric power supply device and consumers and thus of their operating currents, i.e. when current paths are opened and closed by the switching device, the connected consumers can be securely switched on and off.
An electric low-voltage switching device, such as for example a contactor, a circuit breaker, a motor branch circuit or a compact starter, has for switching one or more current circuit(s) one or more so-called main contact(s) or auxiliary contacts which can be controlled by one or even more actuation magnets, i.e. electromagnetic drives. In principle, the main or auxiliary contacts each consist of a displaceable contact, in particular a contact bridge, and a stationary contact or a stationary contact piece, to which the consumer and the supply device are connected. To close and open a main or auxiliary contact, a corresponding on- and off-switching signal is given to the actuation magnet, whereupon this magnet acts with its armature upon the displaceable contact such that the displaceable contact or the contact bridge completes a relative movement in relation to the stationary contact and either closes or opens the current path to be switched.
For improved contacting between a stationary contact and a displaceable contact, appropriately fashioned contact surfaces are provided at points at which the two meet. These contact surfaces consist of materials such as, for example, silver alloys which are applied at these points both on the displaceable contact, i.e. the contact bridge, and on the stationary contact, i.e. the contact piece, and are of a defined thickness.
These mechanical switching devices have, because of the required tolerance of the parts, a tolerance insert by which the resilience of the switching contacts can be adjusted. By way of adjustment, the paths and resiliences can be controlled to a relatively precise degree, as a result of which the magnetic paths in the device can be kept small. This makes it possible to minimize the power loss of the equipment.
Until now, the adjustment of switching devices has been effected by a tolerance insert of different thicknesses, which is inserted into the closed magnet chamber. FIGS. 1 and 2 show this based on the example of a contactor. After assembly of the switching device 1, the paths and resiliences are determined in this example. If these lie outside the desired limit values, the tolerance insert 2 has to be replaced by thicker or thinner tolerance inserts.
This arrangement has the disadvantage that after the switching device 1 has been assembled and gauged, the tolerance insert 2 has to be replaced again. To do this, the switching device 1 has to be dismantled again and reassembled once more, i.e. in order to assemble a different tolerance insert 2 below the spring element 6, which is arranged below the actuation magnet 4, the actuation magnet 4 and the spring element 6 have to be removed from the magnet chamber 3. This is associated with a high outlay in terms of design and time.